With LSI, the high degree of integration of circuits and the scale down of chip sizes have been hitherto realized by pursuing the scaling (shrink) depending on the development of photolithography.
In recent years, however, it has become difficult or impossible to further advance the scaling (shrink) at such a speed as experienced hereinbefore owing to the physical limits of elements and also to the limits of lithography. In view of the fact that the surface of a single crystal silicon substrate that is a land on which semiconductor elements are formed has become so valuable that a remarkable tendency is shown to make elements and wirings by building up on the silicon substrate.
In addition, the high degree of integration and the high degree of functioning of LSI have been recently in progress as typically represented by system LSI wherein memory LSI and logic LSI are loaded as mixed. This entails not only the complication of a manufacturing process, but also the ever-increasing number of steps.